CHICAGO, FEB. 29 -- Officials of the Art Institute of Chicago agreed today to return an 878-year-old stone sculpture to Thailand as long as the Thais replace it with a comparable work of art.

Such a swap is illegal in Thailand, but a group of Thai politicians found a way around the prohibition at a two-hour meeting in Chicago today with Art Institute officials.

If the museum gives up the sculpture, "we would probably give some kind of gift to the Art Institute as a good-will gesture," said Porntep Techapaibul, a member of the Thai parliament who led 13 other legislators to the negotiating session.

"We use the term 'exchange,' " said Larry Ter Molen, the Art Institute's vice president for development and public relations, "but they prefer to call it a gift; so that is the way we will proceed. We would return the sculpture, and they would give us a token of their appreciation."

The sculpture, "The Birth of Brahma with Reclining Vishnu on a Makara," disappeared from the temple of Khao Phanomrung in northeastern Thailand in the 1960s and has been on display at the Art Institute since 1967.

The temple, built between the 10th and 13th centuries, has been restored and is scheduled to open in April. But its appearance is spoiled by the absence of the Vishnu sculpture, carved in 1110, which stretched across a gateway to the main sanctuary.

The Thai legislators said the sculpture has become such a hot political issue in Thailand that they were willing to fly halfway around the world to try to get it back.